Shoe (platform) lumps are quite common on the 1900 era double rifles.
Westley Richards and Webley (i.e Evans, Army Navy, and many other retailers) have used them extensively.
They usually switched to Chopper lumps post 1900 or so.
Shoe lumps are rarely used on shotguns due to the tubes size making the shoe very thin.
The Shoe lump or dovetail lump make it easier to procure and machine raw barrel forgings. Otherwise, you need a left and a right forging.
Best regards,
WC-